fix(client): pad_audio reached for a module name Windows doesn't have

`audio_wasapi.rs` is mounted as `crate::audio` (lib.rs, `#[cfg(windows)]
#[path = "audio_wasapi.rs"] pub mod audio;`), so there is no `crate::audio_wasapi`
path to reach it by. `pad_audio.rs` used one anyway, which means pf-client-core has
not compiled for Windows since 35285afa landed in the pad-audio merge (8983ec04) —
E0433, so every Windows client build on main is red, not just this call site.

Found while validating the FFmpeg bump on the CI runner; unrelated to it, hence its
own commit.

crates/pf-client-core/src/pad_audio.rs

@@ -840,7 +840,7 @@ struct PadOut {
 #[cfg(windows)]
 impl PadOut {
     /// Correlate (HID container → endpoint id) and open a shared event-driven render stream ON
-    /// that endpoint (`audio_wasapi::render_thread`'s shape — autoconvert, default period).
+    /// that endpoint (`audio::render_thread`'s shape — autoconvert, default period).
     fn open() -> anyhow::Result<PadOut> {
         use anyhow::{anyhow, Context};
         let hid_path =
@@ -921,10 +921,10 @@ fn pad_render_thread(
         const BLOCK_ALIGN: usize = PAD_CHANNELS * 4; // f32 interleaved
         let enumerator = wasapi::DeviceEnumerator::new().context("DeviceEnumerator")?;
         // Not `get_device`: that helper resolves through a freed string — see
-        // [`crate::audio_wasapi::device_by_id`].
-        let device =
-            crate::audio_wasapi::device_by_id(&enumerator, &Direction::Render, endpoint_id)
-                .map_err(|e| anyhow!("correlated endpoint not found: {e:#}"))?;
+        // [`crate::audio::device_by_id`]. (`audio_wasapi.rs` is mounted as `crate::audio`
+        // on Windows via `#[path]`, so it has no `crate::audio_wasapi` name to reach it by.)
+        let device = crate::audio::device_by_id(&enumerator, &Direction::Render, endpoint_id)
+            .map_err(|e| anyhow!("correlated endpoint not found: {e:#}"))?;
         let mut audio_client = device.get_iaudioclient().context("IAudioClient")?;
         // FL|FR|BL|BR: front pair = the pad's speaker, back pair = the voice coils.
         let desired = WaveFormat::new(32, 32, &SampleType::Float, 48_000, PAD_CHANNELS, Some(0x33));